U.S. Pat. No. 5,854,621 entitled “WIRELESS MOUSE” discloses a communication system for receiving signals representing displacement action of a peripheral device. The communication system includes a first peripheral device and a receiving unit. The first peripheral device has to include a first non-volatile memory device for storing a first identifier. The receiving unit includes a second non-volatile memory device for storing the first identifier and other authorized identifiers of the peripheral device. Although U.S. Pat. No. 5,854,621 can solve problem of data interference during data transmission and receipt between the peripheral device and receiving unit, the non-volatile memory device has to be used in the transmitting peripheral device for storing the identifier permanently. However, using the non-volatile memory results in increasing production cost and this is deficiency of U.S. Pat. No. 5,854,621.